Greenlee M C, Sullivan S A, Bohlson S S
Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
Curr Drug Targets. 2008 Feb;9(2):130-8. doi: 10.2174/138945008783502421.
CD93 belongs to a newly described family of transmembrane glycoproteins which also includes endosialin and thrombomodulin. These cell surface proteins are grouped into a family based on similar ectodomain architecture consisting of a C-type lectin-like domain, a series of EGF-like repeats and a highly glycosylated mucin-like domain. However, recent studies suggest overlapping functions in the regulation of processes involving innate immunity and inflammation. CD93 regulates phagocytosis of apoptotic cells in vivo, a function critical to development, tissue repair and maintenance of tissue homeostasis. In addition, in vitro studies have demonstrated a role for CD93 in phagocytosis of antibody and complement opsonized particles and also in leukocyte and endothelial cell adhesion. Analysis of CD93 expression on endothelial cells in the developing mouse embryo correlates with the remodeling of blood vessels suggesting a role for CD93 in regulating angiogenesis, a process tightly linked to acute and chronic inflammation and also required for tumor metastasis. Endosialin has been characterized as a tumor specific antigen and functions in angiogenesis. Thrombomodulin is best characterized as a natural anticoagulant; however, more recent reports have illuminated the importance of thrombomodulin in the regulation of inflammation. This review discusses similarities and differences in the family members, and focuses on known and speculated functions in regulation of innate immunity.
CD93属于一个新描述的跨膜糖蛋白家族，该家族还包括内唾液酸蛋白和血栓调节蛋白。这些细胞表面蛋白基于相似的胞外域结构被归为一个家族，其结构由一个C型凝集素样结构域、一系列表皮生长因子样重复序列和一个高度糖基化的粘蛋白样结构域组成。然而，最近的研究表明，它们在涉及先天免疫和炎症的过程调控中具有重叠功能。CD93在体内调节凋亡细胞的吞噬作用，这一功能对发育、组织修复和组织稳态的维持至关重要。此外，体外研究已证明CD93在抗体和补体调理颗粒的吞噬作用以及白细胞和内皮细胞黏附中发挥作用。对发育中小鼠胚胎内皮细胞上CD93表达的分析与血管重塑相关，提示CD93在调节血管生成中发挥作用，血管生成是一个与急慢性炎症紧密相关且肿瘤转移也必需的过程。内唾液酸蛋白已被鉴定为一种肿瘤特异性抗原，并在血管生成中发挥作用。血栓调节蛋白最主要的特征是作为一种天然抗凝剂；然而，最近的报道揭示了血栓调节蛋白在炎症调节中的重要性。本综述讨论了家族成员之间的异同，并着重介绍了在先天免疫调节中已知和推测的功能。
